PFCs are chemicals that are used in many household items, including furniture, cosmetics and food packaging.

"There is no doubt that there is an association between exposure to PFCs and onset of menopause, but the causality is unclear," Sarah Knox, lead author of the study, said in a news release from the university on Wednesday.

Even though the report may not be conclusive, it's still raising eyebrows. Some doctors say they're not surprised that chemicals are altering hormone levels, but they say they need more proof.

Some Doctors Want More Proof

"Studies that we've done looking at these chemicals on the U.S. population show that almost everyone has these chemicals in their blood," Dana Boyd Barr, a research professor at the Rollins School of Health at Emory University in Georgia, told ABC News.

PFCs have long been linked to cancers and thyroid disease in animal studies. The type of PFCs found in nonstick frying pans has been known in rare cases at high heat to kill birds and cause flu-like symptoms in people.

Chemical companies maintain their product is safe, but the study raises questions about whether early menopause is a new reason to worry about PFCs in general.

"PFCs are toxins that shouldn't be in our bodies in the first place, but 98 percent of people tested have measurable levels of PFCs in their blood," Knox, an epidemiologist and professor in the university's Department of Community Medicine, added in the release. "If the PFCs are causing early menopause, then those women are at an increased risk for heart issues. If they aren't, there are still toxins accumulating in the body that shouldn't be there. Either way, it's bad news."

EPA Expressed Concern About PFCs

In the study group of 25,957 women, high levels of PFCs were found in those experience early onset menopause as young as age 42. The women also saw a big decrease in their estrogen levels.

The findings "did not prove whether that is because earlier menopause causes PFC's to be higher or PFCs cause earlier menopause," said Dr. Alan Ducatman, a medical doctor who also participated in the study.

Ducatman said researchers will know more about the causality if they are able to follow the test subjects over time.

The U.S Environmental Protection Agency also has expressed concern about the long-term effects of PFCs in humans and wildlife.